update README version to 0.8.0.0

If a developer discovers `react-rails` through Github, they'll probably use whatever version number is listed on the README. For that reason, most Rails projects keep the README version number up-to-date so that folks don't accidentally install old versions.
Merge pull request #20 from matchu/master

update README version to 0.8.0.0
Add a view helper to render react component.
Introduce react_ujs.

* Implement react_ujs.
* Replace inline scripts with react_ujs style data attributes.
* Update tests and README.
Update JSXTransform test case, fix travis test.

Newer coffee-script generates slightly different output, accept it
in JSX coffee script test case.
Address issues about empty props.

* react_ujs: use `null` instead of `{}` as default props.
* view helper: remove 'data-react-props' if props is empty.
* view helper: allow 'data' in HTML options.
Set `eval` context to `window`.

This allows better minification.
Update README

* Fix a comment about React.renderComponent where the order of arguments is wrong
* Mention that react_ujs will unmount components and how to avoid it
Merge pull request #17 from quark-zju/view-helper

View helper to render react component
Allow react.js and jsxtransformer.js to be overriden by user
Allow user to override jsxtransformer used for .jsx files
Document manual react and JSXTransformer version changing
Allow for drop-in replacement using recommended files structure
Updated docs with right information on changing react's version
Fixed react.js-replacing paths in comments
Rename test asset files due to collisions
Iron out problems left uncaught during rebase
Bump up version to stop being dependent on react versioning
Updated info about drop-in feature in README
readme: fixed info about restarting to bust transformer context cache